The civilian standard for timekeeping has increased its accuracy by a factor of three with the announcement Thursday by the National Institute of Standards and Technology in Boulder of a new atomic clock.
The NIST F-2, which would not gain or lose one second in roughly 300 million years, is about three times as accurate as the NIST F-1.
The NIST F-2 will serve as the United States' new civilian time and frequency standard, along with the F-1.
The enhanced accuracy of timing and frequency standards has broad implications for the greater performance and dependability of modern-age staples such as power grids, global positioning systems, computer networks and cellphone service.
Tom O'Brian, chief of the Time and Frequency Division at NIST, called the new timepiece "the most accurate official atomic clock in the world."
O'Brian said, "We have atomic clocks that are already more precise than NIST F-2. Now, these are research clocks. They are not anywhere near ready to serve as official timekeeping devices yet."
He added, "One of the burdens of being a good atomic clock scientist is that you are aware that the competition is always sort of ahead of you, all the time.
"That's exciting as well. "
NIST plans to operate both the NIST-F1 and NIST-F2 simultaneously, for now. Long-term comparisons of the two clocks will help scientists at the lab continue to improve both clocks as they serve as U.S. standards for civilian time. The U.S. Naval Observatory maintains military time standards. The NIST-F1 has served as the exclusive standard for such technology since 1999.
"We're terribly imaginative about our names around here," NIST physicist Steve Jefferts, lead designer of NIST-F2, joked. He added, "F-2 is really a refinement on NIST F-1. They are very similar clocks in a lot of ways, at least if you look at the big picture."
Both clocks use what is termed a "fountain" of cesium atoms to determine the exact length of a second.
"Nothing here is going to change the way we live tomorrow, in terms of having a three times more accurate clock," Jefferts said. "But these technologies keep getting adopted for use in our society, so we have to keep inventing things to make them work better, because people keep using them."
'My best guess is, this is it'
Both the NIST-F1 and NIST-F2 measure the frequency of a particular transition in the cesium atom — which is 9,192,631,770 vibrations per second, and is used to define the second, the international unit of time.
The key operational difference is that F1 operates near room temperature, about 80 degrees, whereas the atoms in F2 are shielded within a much colder environment, about -316 degrees. That cooling significantly lowers the background radiation, reducing some of the very small measurement errors that must be corrected in NIST-F1.
The latest iteration of NIST's atomic clock might represent the outer limits of the capacity for that specific technology, Jefferts said.
"I would say my best guess is, this is it," he said. "We'll make F-2 a little bit better, add that 10 percent here, and 20 percent there. But you're not going going to see another (improvement) factor of three or 10 out of cesium.
"But I should be careful, because my colleague who built NIST-7 (in 1993), which was the last old-style cesium clock, said the same thing about it 20-some-odd years ago... because he hadn't been able to anticipate the invention of laser-cooled cesium clocks.
"So if a technological revolution comes along that I'm not anticipating, I suppose we could see another (improvement) factor of 10."
Looking ahead to redefining time, itself
Also during Thursday's press conference, Jefferts said, "Not so far in the future, we're going to end up redefining the second, in terms of these optical clocks that are now research devices.
"And when we do that, we need to be able to make the transition from the use of cesium as the definition of the second, to the use of some optical standard, that hasn't been determined yet... That redefinition is not NIST's job. That's a thing that happens at the international metrological community level, and so it will require a whole bunch of people agreeing, for that to happen."
O'Brian posed Jefferts a question of his own Thursday, querying him on what will take the place of laser-cooled cesium clocks.
"It's going to be one of the optical standards, and I would say at the moment it's a really interesting horse race. There is, I don't know, on the order of 10 candidates out there and it sees like every six months somebody has pushed a new candidate into first place.
"And at the end of the horse race I think all those clocks are going to be so good that we're going to have to really change our conception of what we mean by ' time,' in the sense that we're going to have to start worrying about space-time, instead of just time, which is a philosophical argument, as well."
O'Brian pointed out that "Cesium clocks 'tick,' quote unquote, at about 10 billion cycles a second. The optical clocks tick at about a million billion cycles per second," giving optical clocks about 100,000 times more 'ticks,' per second."